Theorists in developmental, clinical, and personality/social psychology have debated the role of individual differences in both emotionality and regulation in social an emotional functioning. Based on theory and gaps in the empirical literature, the purposes of the proposed research are to examine the additive and interactive contributions of individual differences in regulation and emotional reactivity to children's socioemotional functioning and behavior. Aspects of functioning and behavior of focal interest include: (a) the occurrence, intensity, and/or duration of directly induced emotions (e.g., anger, sadness); (b) occurrence and intensity of vicariously induced emotion to others in distress or need (sympathy and personal distress); clarity of expression of negative and positive emotions and the tendency to monitor one's own expression of emotion and behavior; (d) socially appropriate behavior and peer acceptance, and (e) problem behaviors and shyness. A secondary goal is to obtain data on the relations of children s emotionality, regulation, and social functioning to the expression of emotion, A multimethod approach will be used, involving self-report and behavioral measures, facial and physiological markers of emotion, and naturalistic as well as laboratory studies. Two studies will be follow-up of longitudinal sample. Dispositional emotionality and regulation will be used as predictors of socioemotional functioning. Emotionality and regulation are assessed with adult and child reports, behavioral and/or physiological measures. Prediction within and across time will be examined. In a related study, similar issues will be examined with a sample that includes children with moderate levels of internalizing and externalizing symptoms. In a fourth study, dispositional correlates of children's expressions of overt emotion with peers will be examined using naturalistic methods. The results of the proposed research would expand and complement our current understanding of the role of dispositional factors and socialization in emotional and social development in childhood. In addition, the research would have implications for understanding the roles of regulation and emotion in behavior problems and change and stability in the development of socially competent, emotionally regulated behavior.